Air heating gas burner



Jan- 10, H, R MAXON, JR ETAL AIR HEATING GAS BURNER 2 Sheets-$l1eet l Filed Feb. 26, 1964 r J S n m o m TMY n W. M UH V .|T| m w 6 Wm I MR 6 H 2 6 Y C B 2 6 rm 6 A QM, W30 W Afiys.

Jan. 10, 1967 MAXQN, JR" ET AL 3,297,259

AIR HEATING GAS BURNER Filed Feb. 26, 1964 2 Sheets-Sheet 2 mfi E a a a @37 5 O 092 5 5 E5 0 a a O O 740. %4b 5 73@ O O O O INVENTORS Harry R. Mflxon Jr Roberr H.Yeo

United States Patent 3,297,259 AIR HEATING GAS BURNER Harry R. Maxon, Jr., and Robert H. Yeo, Muncie, Iud., assignors to Maxon Premix Burner Company, Inc., Muncie, Ind., a corporation of Indiana Filed Feb; 26, 1964, Ser. No. 347,514 20 Claims. (Cl. 239-3975) The present invention relates to gas burner systems and, more specifically, to gas burners adapted to be disposed in and to heat an air stream.

It is an object of the present invention to provide a gas burner which is especially adapted for operation in and for heating an air stream that supplies all or a substantial percentage of the oxygen required to assure complete combustion, the amount of oxygen used depending upon whether the burner fuel comprises raw gas or a gas air mixture.

It is another object of the present invention to provide an .air heating gas burner that has a wide turn-down ratio, i.e., a high ratio between its maximum and minimum firing rates and, further that can be readily adjusted over its entire operating range with a smooth and continuous variation in its heating output.

It is a further object of the present invention to provide an air heating gas burner that is specifically an improvement over the type of gas burner disclosed in the Ye'o et al. Patent No. 3,051,464.

It is yet a further object of the present invention to provide a new and improved gas burner that is adapted to operate in and heat an air stream by utilizing a small amount of the air stream to effect at all firing rates, i.e., low, intermediate, and high, complete stoichiometric combustion of the burner fuel whether raw gas or a gas-air mixture.

It is still another object of the present invention to provide an air stream burner having improved flame retention properties and high quality combustion characteristics when raw gas is used as the burner fuel.

It is yet another object of the present invention to provide a gas burner that is adapted to operate at a substantially lower minimum firing rate having better operating characteristics than comparable prior art burners.

It is another object of the present invention to provide an air-stream gas burner that is constructed so as to provide a flame pattern at minimum firing rates that embodies improved flame characteristics.

It is still a further object of the present invention to provide an air stream gas burner that produces at minimum firing rate a flame having improved appearance and greater stability.

It is another object in accordance with the previous object to provide a burner that retains flame throughout the. entire burner at intermediate firing rates, so that the burner fuel is prepared for combustion over a wider range of firing rates than obtainable in prior art burners.

It is still another object of the present invention to provide an air stream gas burner that has controlled thermal expansion characteristics.

It is another object in accordance with the previous object to embody the thermal expansion feature in a mixing plate structure that effects the mixture of air from the passing air stream and the burner fuel.

It is another object of the present invention in accordance with any of the previous objects to provide a gas burner that is easily and inexpensively manufactured and, in addition, that requires reduced maintenance expense.

The above and other objects are achieved in accordance with the present invention by providing a gas burner system adapted to heat an air stream moving at a desired velocity. More specifically, the air stream system embodies a gas burner adapted to be disposed within and to heat an air stream by utilizing a portion of the air stream to effect complete combustion of the burner fuel, i.e., either raw gas or gas-air mixtures. The burner is so constructed that it has a high or wide turn-down ratio, i.e., a high ratio of maximum to minimum firing rates and further, it can be readily throttled over its entire range of operation with a smooth and continuous variation of its heat output. More specifically, the gas burner embodies a burner body means and a mixing plate means supported from the burner body means.

In one aspect of the invention, the burner is so constructed that a thoroughly controlled progressive aeration occurs continuously and smoothly from low to high firing rates. To this end, the burner has improved minimum flame characteristics, i.e., a lower minimum firing rate, an improved flame appearance, and better flame stability. In addition, flame is retained adjacent the burner casting throughout intermediate and some high firing rates, so that the burner fuel is prepared for combustion over a greater range of firing rates than possible with prior art burners. In another aspect of the invention, the burner has controlled thermal expansion characteristics and, to this end, the mixing plate means is preformed to permit predetermined and controlled expansion, thereby permitting the mixing plate means to contract to its original position and avoiding permanent distortion or warpage.

The invention, both as to its organization and method of operation, taken with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of an air stream heating system including a gas burner embodying the features of the present invention, the gas burner system being illustrated as being used with raw gas;

FIG. 2 is an enlarged fragmentary perspective View of one embodiment of the gas burner of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary perspective view, from a different vantage point than FIG. 2, of the burner of FIG. 2;

FIG. 5 is a diagrammatic view of the flame pattern at minimum firing rates developed by the burner of FIG, 2;

FIG. 6 is an enlarged fragmentary side elevational view of the burner of FIG. 2;

FIG. 7 is a top plan view of a single mixing plate embodied in the burner of FIG. 2;

FIG. 8 is a sectional view taken along lines 8-8 of FIG 6; I

FIG. 9 is a sectional view, similar to FIG. 3, of another embodiment of the gas burner of FIG. 1; and

FIG. 10 is a diagrammatic view of another form of the air stream heating system of FIG. 1, the gas burner system being illustrated as used with -a gas-air mixture.

Referring now to the drawings, there are illustrated burner systems embodying air stream gas burners adapted to be supplied with either type of burner fuel; i.e., either raw gas or a gas-air mixture. More specifically, there is illustrated in FIG. 1 a burner system 10 of the type adapted to be used with raw gas, while there is illustrated in FIG. 10 a burner system of the type adapted to be used with a gas-air mixture. Without in any way limiting the scope of usage of the system 100, it has particular utility in (1) heating make-up air for factories and other manufacturing and processing establishments, supplying heated air for ventilating and other processes and/ or supplementing the normal space heating facilities, (2) heating air for industrial ovens and similar facilities in which recirculating hot-air-in-motion is used as a processing medium for drying, baking, curing, tempering,

above identified installations Nos. 1 and 3. tern 10 is used with the above identified installation No. ,2, auxiliary air or oxygen necessarily has to be supplied and other similar industrial and commercial processes, and (3) heating air in simple non-recirculating drying applications. Without in any way limiting the scope of usage of the system 10, it has particular utility in the If the systo the system, because in a closed recirculating system all of the oxygen in a relatively short time is consumed in the combustion process.

The systems 10 and 100, as illustrated in FIGS. 1 and 10 respectively, are generally similar in construction,

with the exception that the system 100 embodies a premixer arrangementlll) for producing the desired gasair mixture. In all other respects, the systems are identical. More specifically, the system 10 includes an air stream 12 conveyed through a duct 14 past a gas burner 16 under the control of a blower 18. The air stream 12 may be either. a fresh air stream, for example, wherein the duct 14 is connected to a fresh air inlet grill 20, or the airstream may be a recirculating stream, for example, wherein the duct 14 is part of a recirculating duct arrangement of an industrial oven or the like and suffi- .cient fresh air or oxygen to permit complete combustion is added to the recirculating stream at a point not shown. In either event, the velocity of the air stream in the duct is determined by the type and size of the blower 18 and/ or by profile plates extending between the burner 16 and the duct 14. Thus, in accordance with the demands and requirements of the particular installation, the air stream velocity is set at aparticular value within the rangeof approximately 1,500 to 4,000 feet per minute. It should be understood, of course, that the blower 18 may be located either on the upstream or downstream side of the burner 16.

As set forth in the above referred to Yeo et al. Patent No; 3,051,464, the gas burner 16 is made up of burner :lements or units forming a desired pattern across the area of the duct. The heating flame occurs in a substan- .ially continuous line or band along the length of each )urner unit and the burner shown distributes the flame lnd heat in a desired pattern across the air stream 12. the gas burner 16 is supported by means (not shown) rentrally within the duct 14 in transverse relationship the moving air stream, whereby the air stream is subtantially uniformly heated by the burner 16. As illus rated in FIG. 1, the burner 16 is connected to a supply [no 22 which, in turn, is connected to a raw gas line 24. "he pressure and/ or velocity of the raw gas supplied to he burner 16 is varied and controlled by any suitable Jeans (not shown), for example, by a valve or the like, efl ect a wide range of firing rates, e.g., low interlediate, and high firing rates.

Similar to the system of FIG. 1, in the system 100 n air stream 112 flows through a duct 114 past a gas urner' 116 under the control of a blower 118. For all ractical purposes, the air streams 12 and 112, the ducts 4 and 114, the burners 16 and 116, and the blowers 8 andx118 are respectively identical in construction. Ioiv ever, in contrast to the system 10, the system 100 nbodies a gas-air premixer arrangement 110 which is litably connected to the gas burner 116 by a supply line 22. It should be appreciated that premixing arrange-1 entsQother than that illustrated and described herein- 'ter, e.g., inspirators or proportional mixers, may also used. The illustrated premixing arrangement 110 has gas inlet pipe 124 andan air inlet shutter 126 and is lapted not only 'to supply regulated amounts of gas-air ixture, but also to control the proportions of gas and r in the mixture and to provide different proportions in e mixture at different rates of mixture supply.

Considering now the gas burner, per se, embracing the atures of the present invention, one embodiment of 5 gas burner is illustrated in FIGS. 2 through 8 and identified generally by reference numeral 16, and an other embodiment is illustrated in FIG. 9 and is identified by reference numeral 216. Each of the gas burners 16 and 216 embodies means that provide a thoroughly controlled progressive aeration continuously throughout the low, intermediate, and high firing rates. To this end, there is provided improved minimum flame characteristics that provide an improved flame appearance and greater flame stability at minimum firing rates. In fact, under comparable conditions, each of the burners 16 and 216 is capable of operating at a substantially lower firing rate having better operating characteristics than comparable prior art burners. Moreover, at intermediate and some high firing rates, the flame in the burners 16 and 216 is nested or retained adjacent the burner surfaces, so that the burner fuel is prepared for combustion under a substantially greater range of firing rates than obtainable with prior art burners. Because of this feature, purging or displacement of the flame forwardly Within the burners 16 and 216 occurs at firing rates higher than that of prior art burners. In addition, each of the burners 16 and 216 has controlled thermal expansion characteristics that provide predetermined and controlled thermal expansion during operation of the burner, with the result that the burner returns to its original position in an undistorted or unwarped condition. As previously suggested, each of the burners 16 and 216 is adapted to be used with either of the systems 10 and and consequently each is adapted to be used with either kind of burner fuel; i.e., raw gas or a gas-air mixture.

Without indicating an order of preference, the gas burner 16 illustrated in FIGS. 2 through 8 will be first described as used, for example, with raw gas. Briefly, the gas burner comprises an elongated burner body or casting 30 that manifolds the raw gas to spaced-apart ports 42 through which the raw gas issues. Supported from the casting 30 is a pair of generally diverging mixing plates 3234 that effect complete combustion of the raw gas at all firing rates between low and high firing rates, in a manner taught by the above Yeo et al. Patent 3,051,464. The burner 16 is disposed within the air stream so that the casting 30 (the rear of the burner 16) is upstream of the mixing plates 32-34 (the front of the burner 16). As illustrated in FIG. 1, the casting 30 faces upstream in opposition to the direction of flow of the air stream, and the plates 32-34 face or open downstream in the direction of flow of the air stream. As a result, the casting 30 divides the air stream and directs it along the casting (to the right as viewed in FIG. 1) onto the upstream surfaces of the mixing plates 3234. The plates 32-34, as best seen in FIG. 2 are apertured so that a part of the air stream passes in the form of inwardly and forwardly directed air jets into a mixing space 35. By this arrangement, thoroughly controlled progressive aeration occurs throughout the entire range of the burner, i.e., that raw gas issuing from the gas ports 42 is intimately mixed with the jets of air to effect a highly controlled and complete combustion of the burner fuel throughout the entire firing range of the burner 16.

Referring now more specifically to the constructional details of the gas burner 16, attention is invited particularly to the burner casting 30, best illustrated in FIGS. 2 and 3. As shown, the casting 30 comprises a manifold section 36 forming a fuel conduit having at its opposite ends attachment flanges 38. The manifold section 36 is generally tear-shaped in cross section and has formed on its downstream side a generally flat wall 40. It should be appreciated that the Wall 40 could alternatively be slightly concave or convex. The gas ports 42 are disposed in a row longitudinally along the center of the wall 40 so as to communicate with the fuel conduit or' mainfold section 36, although it should be understood tour to the airstrearn and is connected to the wall 40:

by a pair of converging, generally flat wall sections 46 and 48. The front end of the casting 30 is notched, as indicated at 47-49 in FIG. 3 to provide a pair of generally parallel walls 51-53 that support the mixing plates 32 and 34. As a result, the air stream engages the generally cylindrical upstream section 44, passes around the section 44, flows forwardly along the converging sections 46-48 and passes onto and along the mixing plates 32 and 34.

As clearly shown in FIGS. 2 and 3, the mixing plates 32 and 34 are each generally angulated so as to define respectively flanges 50 and 52 which are respectively secured by fasteners 55 to the generally parallel walls 51-53. Extending forwardly and comprising a continuation of the flanges 50 and 52 are generally parallel sections 54 and 56 that define part of the mixing space 35. Angularly related to the sections 54 and 56 are sections 58 and 60 that diverge forwardly and outwardly relative to the burner casting 30 to define a trough-shaped part of the mixing space 35.

In accordance with the previously discussed progressive aeration concept, each of the mixing plates 32 and 34 is provided with rows of spaced-apart apertures 61 through 78, as best seen in FIGS. 2, 4, and 6. The apertures 61 are the smallest, while apertures 62 through 78 are progressively larger in size, thereby providing (from the rear to the front of the burner) progressively larger air jets that are directed inwardly and forwardly into the mixing space 35. In addition, the apertures 61 and 62 in the sections 54 and 56 are staggered and offset relative to one another, as described in greater detail hereafter, to provide a zipper flame pattern. Similarly, the apertures 63 through 78 in the sections 58 and 60 are likewise staggered and offset relative to one another, such that the air jets issuing through these apertures 63 through 78 in the sections 58 and 60 do not impinge against one another but are displaced relative to one another. It will be appreciated that the apertures 61 through 78 can assume different configurations, but in the form shown all of the apertures 61 through 69, 72, 73 and 78 are circular and are simply stamped out of the plates 32 and 34. The apertures 74a, 75a, 76a, and 77a are also circular and are simply stamped out of the plates 32 and 34. On the other hand, apertures 74b, 75b, 76b, and 77b are generally rectangular and each is formed by a die of appropriate construction that produces a tongue 79 extending outwardly from and generally perpendicular to the plates 32 and 34. In this position, the tongues intercept air from the air stream and direct it through the apertures. As a result, somewhat more air passes through the rectangular apertures 741; through 77b then passes through circular apertures 74a through 77a. As shown in FIG. 6, the rectangular apertures in each of the plates 32 and 34 are arranged in two spaced-apart, generally triangular groupings. To this end, there is provided only one generally rectangular aperture 74b, a pair of closely spaced rectangular apertures 75b, a pair of more generously spaced rectangular apertures 76b, and three generally rectangular apertures 77b. The pair of generally triangular groupings are separated by three circular apertures 74a, two circular apertures 75a, two circular apertures 76a, and one circular aperture 771:. As shown, a single circular aperture 74a, 75a, 76a, and 77a is provided on the left and rigid side (as viewed in FIG. 6) of the triangular groupings of the rectangular apertures.

The apertures 70 and 71 are arranged, for example, in each of the plates 32 and 34 in the pattern best illustrated in FIG. 6. The apertures 70 and 71 are formed by embossments 80, seen best in FIG. 8, and hereafter are ferred to as embossed apertures 70 and 71. These embossed apertures 70 and 71 perform a flame retention function and improve the flame stability and appearance at intermediate and high firing rates. Actually, 'because of the embossed character of the apertures 70 and 71,

an improved vacuum is developed adjacent the apertures 70 and 71 so that more gas is drawn into the air jets issuing through the apertures 70 and 71. The apertures are generally semi-conical and have a cross-section best illustrated in FIGS. 3 and 8. As a consequence, the air passing through the embossed apertures 70 and 71 is, in a sense, compacted or restricted by the converging shape of the embossment 80, thereby producing a relatively high velocity air jet. Hence, the air jet or protrusion jet penetrates more directly into the middle of the mixing space 35 thereby assuring intimate mixture of the air with the gas issuing through the ports 42. As a result, the flame developed at intermediate and high firing rates is thereby nested or disposed more closely adjacent the mixing plates 32 and 34 to reduce the flame length and produce a better flame appearance.

By the use of the apertured mixing plates 32 and 34, as the air stream moves forwardly over the mixing plates 32 and 34, portions of the air stream pass into the apertures 61 through 78 to produce air jets that (1) develop vacuum pockets for drawing gas issuing through the ports 42 forwardly along the inner faces of the mixing plates 32 and 34 and (2) effect intimate mixture of the air from the air stream with the gas issuing through the ports 42, in a manner clearly described in the above identified Yeo et al. patent. Hence, irrespective of the velocity of the burner fuel required for a designated firing rate, the standing array of air jets (developed by apertures 61 through 78) provides for controlled progressive aeration to assure stable and complete combusion of the gas between the plates 32 and 34. Actually, the air jets passing through apertures 61 of the sections 54 and 56 and the apertures 62 of the sections 54 and 56 each produce a zipper flame pattern that effects complete combusion of the gas at low firing rates, whereas the air jets passing through apertures 63 through 78 progressively assure complete combustion of the gas at firing rates progressively higher than low firing rates, for example, intermediate firing rates and high firing rates.

Considering now one aspect of the present invention in greater detail, and referring particularly to the zipper flame pattern developed at low firing rate, attention is invited to the sections 54 and 56 of the mixing plates 32 and 34. By the proper location and spacing of the apertures 61 and 62 relative to one another and relative to the ports 42, a greatly improved minimum flame characteristic is obtained. As indicated above, a much lower firing rate, improved flame appearance and greater flame stability than previously obtainable with prior art burners is obtained by applicants invention. As illustrated best in FIGS. 2, 4, 5, and 6, the apertures 61 and 62 on plate 58 (as seen in FIG. 6) are vertically displaced or offset relative to one another. The apertures 61 and 62 in the mixing plate 34 are likewise vertically displaced or offset relative to one another. However, the apertures 61 in the plates 32 and 34 are out of alignment or are horizont-ally displaced or offset relative to the gas ports 42 as best seen in FIGS. 4 and 5. As a result of this disposition of apertures 61 and 62 and ports 42, a zipper flame pattern is developed at low firing rates.

Referring more specificially to FIG. 5, it is a diagrammatic view of the zipper flame pattern that occurs at low firing rate. Actually, in order to facilitate understanding of the zipper flame pattern, the apertures 61a,

61b, and 610 in the plates 32 and 34 (i.e., located on the left) are slightly displaced to the left in FIG. 5, whereas apertures 62a, 62b, and 620 (i.e., located on the left) are illustrated in their proper positions. The air jets issuing through apertures 61a, 61b, 61c, 62a, 62b and 620 are illustrated by arrowed lines so that the path of the air jets only can be identified. On the other hand, in the middle and right end of FIG. 5, the apertures 61 and 62 are located in their proper position and the true flame pattern (including the mixing air jets and gas) is depicted as it appears from the forward end of the burner.

As shown in both FIGS. 4 and 5, the air jet issuing through the aperture 610 in the plate 32 is identified by reference numeral 81 and extends downwardly as viewed in FIG. 5. The air jet 81 is directed toward and is intercepted. by an imperforate portion of plate 34 so as to be divided into two paths extending to the left and to the right as shown in FIG. 5. On the other hand, the air jet issuing through the aperture 61b in the plate 34, identified .by reference numeral 82, extends upwardly as viewed in FIG. 5. The air jet 82 is directed toward and intercepted by animperforate portion of the plate 32 so'as to be divided into two paths directed to the left and to the right as viewed in FIG. 5. The air jet issuing through apertures 61c in the plate 32, identified by reference. numeral 83, extends downwardly as viewed in FIG. 5. The air jet 83 is directed toward and is intercepted by animperforate portion of the plate 34 so as to be divided into two paths directed to the left and right as viewed in FIG. 5. It will be noted that the air jets 81 and 82 (issuing through apertures 61a and 61b) are located to the side of and equidistantly spaced from the gas port 42a; in the same manner the air jets 82 and 83 (issuing through apertures 61b and 610) are located on the side of and equidistantly spaced from the gas port 42b. This pattern of alternate, oppositely directed, displaced air jets exists throughout the first row of air jets in both of the plates 32 and 34.

The same orientation of air jets issues through apertures 62 in the plates 32 and 34, except that the direction of the air jets issuing through apertures 62 is opposite to the air jets 81, 82, 83, etc., issuing through apertures 61. More specifically, the air jet issuing through aperture 62a in the plate 34, identified by reference numeral 84 extends upwardly as viewed in FIG. 5. The air jet 84 is directed toward and is intercepted by an imperforate portion of plate 32 so as to be divided into two paths extending to the left and the right as viewed in FIG. 5. On the other hand, the air jet issuing through the aperture 62b of the mixing plate 32, identified by reference numeral 85, extends downwardly as viewed in FIG. 5. The air jet 85 is directed toward and is intercepted by an imperforate portion of the plate 34 so as to be divided into two paths extending to the left and right as viewed in FIG. 5. The air jet issuing through the aperture 62c of the mixing plate 34 is identified by reference numeral 86 and extends upwardly as viewed in FIG. 5. The air jet 86 is directed toward and is intercepted by an imperforate portion of plate 32 so as to be divided into two paths extending to the left and right as viewed in FIG. 5.

It will be noted that the air jets 84, 85, and 86 issuing through apertures 62a, 62b, and 620 are equidistantly spaced from the gas ports 42. As a result, gas issuing through the port 42b for example is essentially ringed by air jet 82 (issuing through aperture 6117) by air jet 83 (issuing through aperture 61c)both of these jets being in the first rowby air jet 85 (issuing through aperture 62b) and by air jet -86 (issuing through aperture 62c) the air jets 85 and 86 being in the second row. Inasmuch as the air jets create vacuums, the gas issuing through the burner port 42b at low firing rate is drawn toward air jets 82, 83, 85, and 86, with the result that the air and gas mix and combustion occurs along the paths defined by these air jets. As one views the gas ports 42b from the forward end of the burner, at low firing rate a zipper flame pattern is observable, as depicted in the right portion of FIGS. Expressed another way, the air jet pattern causes a mixture of air and gas to be formed as shown in the left portion of FIG. 5, and thereby form ribbons of flame in the paths depicted in the right portion of FIG. 5. Actually, the jets may be said to interlace or interweave to produce in essence a zipper appearance.

By the use of the zipper flame pattern, improved minimum firing characteristics are obtainable, i.e., the rninimum firing characteristics of the present burner are substantially improved over prior art burners. First, under comparable operating conditions, the burner of the present invention is capable of operating at a much lower firing rate than comparable prior art burners. As a result, a significant broader operating range and substantially high er turn-down ratio is obtained. Second, the flame at minimum fire has greater stability and has a predetermined and orderly appearance, a standardusually applied by operators of the burners. While the zipper flame pattern causes a less rapid diffusion or movement of the gas toward the air jets than a direct impingement or turbulent method, the offset apertures and gas ports produce more positive and definite paths for the mixing of the air and gas. Third, production of carbon monoxide is virtually eliminated, with only traces of the order of two or three parts per million measurable at any firing rate. Such performance is almost ideal and well within the codes. Fourth, the flame is purged or displaced outwardly onto the mixing plates 32 and 34 at a substantially higher firing rate than obtainable with prior art burners.

portions 94 and 96 permit the mixing plates to thermallycontrolled thermal expansion.

For example, in the prior art burners that embody. a direct impingement concept, i.e., the air jets are opposite to one another to directly engage or intercept one another, the flame is purged at a lower firing rate. With applicants burner, the flame is retained adjacent to the gas ports 42 throughout a substantially wider operating range and therefore (1) a significant percentage of the gas, e.g., 510%, at intermediate firing rates is burned in the vicinity of the gas ports 42 and (2) the gas issuing through the ports 42 is preheated and vdiffused to better condition the gas for subsequent combustion in the mixing space 35.

From the foregoing description, it should be appreciated that the controlled progressive aeration feature is obtained by proper sizing and location of the apertures 61 through 78 in the mixing plates 32 and 34. One of the significant advantages of the burner of the present invention is that the firing rate of the burner can be smoothly and continuously changed throughout its entire range, i.e., the burner does not have any points of flame instability or flame discontinuity so that infinitely variable heat generation is provided.

In accordance with another aspect of thepresent invention, the mixing plates 32 and 34 have controlled thermal expansion characteristics. In prior art burners, it.

is well known that the heat generated by the burner causes its mixing plates to heat up and expand. When the burner is turned olf and is cooled, the burner plates do not always return to their original position, with the -result that the mixing plates experience distortion and warpage which is undesirable to the owner or operator of the burner.

To avoid these undesirable results, the mixing plates 32 and 34 are preformed to permit predetermined and Specifically, and considering only section 58 of the mixing plate 32 disclosed in FIG. 6, it is stamped into the configuration best shown in FIGS. 6 and 7. More specifically, the plate section 58 includes an outwardly and forwardly extending ridge 92. formed by a. pair of inclined, generally triangular ex-,

pansion portions 94 and 96, the sections 94 and 96 increasing in width from the rear to the front of the burner or mixing plate 34. As shown, the triangular sections terminate at the junction of the sections 54 and 58. By

the use of such construction, when the burner is operated at a high firing rate for a period of time during which the plates 32 and 34 might become heated, the expansion expand in a predetermined outward direction. Conversely, when the mixing plates .cool, thermal contraction is controlled, with the result that the plates 32 and 34.

return to their original configuration shown in FIGS..6 and 7. Itshould be appreciated that the mixing plates that embody the controlled thermalexpansion feature may embody configurations other than that previously described and illustrated in FIGS. 6, 7, and 8. For example, the outwardly and forwardly extending ridge may be shorter than the ridge 92 in the plate 32, whereby the associated triangular expansion portions are smaller than the expansion portions 94 and 96 on the plate 32. Secondly, the width of the base of the triangular expansion portions may be shorter than the widths of the bases of the expansion portions 94 and 96 of the plates 32. Thirdly, more than one outwardly and forwardly extending ridge and associated triangular expansion portions may be employed in each of the mixing plates.

In the event that the rearward portion of the mixing plates 32 and 34 become heated during higher firing rates, provision is made for their expansion and contraction. In this connection, slots 98 are defined adjacent the flanges 50 and 52 of the plates 32 and 34 so that movement of the plates 32 and 34 is possible relative to the fasteners 55 and the casting walls 51 and 53.

While the burner 16 has been described as being operable with raw gas for example, in a system similar to system 10, it should be understood that the burner 16 can also be used with an air-gas mixture, for example, in a system similar to the system 100.

The gas burner 216 illustrated in FIG. 9 is structurally and functionally substantially identical to the burner 16. To this end, the burner 216 embodies the controlled progressive aeration feature and the controlled thermal expansion feature. However, in contrast to the gas burner 16 in which the low fire apertures 61 and 62 are embodied in the mixing plates 32 and 34, the low fire apertures in the burner 216 are embodied in the burner casting itself. More specifically, the burner casting 230 as shown in FIG. 9 embodies a manifold section 236 forming a gas conduit having attachment flanges 238 at its ends. The manifold section 236, similar to the manifold section 36, is generally tear-shaped in cross section with the exception of its downstream end. Instead of the front end of the burner casting 230 having a flat end or face (similar to the end wall defined between the walls 51 and 52) the front end 233 is recessed to define a pair of generally parallel extensions 254 and 256. The extensions 254 and 256 comprise extensions of support walls 250 and 252. Apertures 261 and 262 are defined, respectively, in each of the extensions 254 and 256, in the same general manner as the apertures 61 and 62 are defined in the sections 54 and 56 of the mixing plates 32 and 34. Moreover, apertures 263 through 278 are defined in the sections 258 and 260 of the mixing plates 232 and 234, in the same general manner as apertures 63 through 78 are defined in the sections 58 and 60 of the mixing plates 32 and 34. The mixing plates 232 and 234 also embody the controlled thermal expansion feature and, to this end, are preformed in the same manner as the plates 32 and 34. In all respects, the operation and function of the burner 216 is identical to the operation and function of the burner 16 and, similar to burner 16, may be used in either system or 100 with either raw gas or premixture, respectively.

While the embodiments described herein are at present considered to be preferred, it is to be understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modifications and improvements that fall within the true spirit and scope of the invention.

What is desired to be claimed in United States Letters Patent is:

1. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of jets, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets, apertures at the same distance from the fuel ports being staggered so that each air jet is directed toward and intercepts an imperforate portion of said one means, whereby the air jets substantially ring the fuel jets to form a pattern of interlacing flames having a zipper appearance.

2. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of jets, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets, said apertures being in rows pairs of which are substantially equidistantly spaced from the fuel ports, the apertures in opposite rows located adjacent said ports being staggered to cause adjacent air jets to pass in opposite directions along opposite sides of the fuel jets so as to form a pattern of interlacing flames having a zipper appearance.

3. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of fuel jets, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, and aperture means in one or both of said means defining rows of air jets, at least the apertures in opposite rows adjacent said ports being staggered so that the air jets are directed past the fuel jets, intercepted by imperforate portions of said one or both means, move along said imperforate portions so that the fuel jets are substantially surrounded by air, thereby providing a pattern of interlacing flames.

4. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of jets, generally diverging mixing plate means supported from said body means extending generally obliquely forward and outward from said burner body means, said plate means defining a forwardly widening trough-shaped mixing space forwardly of said fuel ports, said mixing space being forwardly wide open for free and open discharge communication with the passing air stream, said mixing plate Walls projecting laterally of said burner body with their back faces positioned to lie exposed to the air stream flowing past the burner, means defined in one or both of said means and including substantially oppositely facing sections that define a low fire mixing zone, means in said sections defining a plurality of apertures through which air from the air stream passes to produce air jets passing by opposite sides of the fuel jets, the distance between said oppositely facing sections being such that the air jets extend across the low fire mixing zone and intercept imperforate portions of said sections to cause the fuel jets to be substantially surrounded by the air of said air jets, whereby a pattern of interlacing flames is provided.

5. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of-apertures through which air from'the air stream passes to produce an array of air jets directed into the mixing space, said mixing plate means being of substantially planar construction having preformed non-planar sections to permit predetermined and controlled thermal expansion, so that after the burner has been operated and the plate means heated, the plate means automatically assume their original position.

-6. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing platemeanssupported from said body means to define a mixing space substantially within which said burner fuel and air from the. air stream are intimately mixedto obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce an array of air jets directed into the mixing space, said mixing plate means having a generally planar construction provided with preformed non-planar structure that is adapted in response to increased temperature to become more non-planar in a predetermined and controlled manner, thereby avoiding an unsightly warped appearance after operation of the burner.

7. A high turn-down gas burner adapted to be disposed in and to heat an air'stream, comprising burner body means, burner fuel ports defined in said burner body means, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce an array of air jets directed into the mixing space, said mixing plate means being substantially planar and comprising a plurality of sections each of which is preformed to have a peaked portion forming a bellows-like structure that permits the section to thermally expand in a predetermined and controlled manner and contract to its original position without experiencing warpage.

8. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce an array of air jets directed into the mixing space, said mixing plate means being substantially planar and comprising a plurality of sections each of which is angulated to provide a peaked portion permitting thermal expansion and contraction of the section without causing permanent warpage.

9. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means defining in said plate means a plurality of apertures through which air from the air stream passes to produce air jets directed toward the burner fuel issuing through the fuel ports, and protrusion means associated with certain ones of said aperture means for providing protrusion air jets to direct greater. quantities of air farther toward the middle of said mixing space than obtainable with aperture means of corresponding size, said protrusionmeans also providing a vacuum greater than that b- 12 tainable with aperture means of corresponding size on the plate means to draw to and hold on the surface of the plate means the burner fuel passing through said ports, whereby the flame pattern remains adjacent the plate means throughout intermediate and high firing rates.

10. The burner of claim 2 wherein there is additionally provided protrusion means associated with certain rows of said aperture means for guiding air from the air stream directly into the flame pattern at intermediate and high firing rates.

11. The burner of claim 1 wherein certain ones of said aperture means are provided with sleeve means for directing air from the air stream directly toward the fuel issuing through the fuel ports to effect more complete combustion of the fuel at intermediate and high firing rates.

12. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets, apertures at the same distance from the fuel ports being located so that each air jet is directed toward and intercepts an imperforate portion of said one means so that air from the air jets substantially surrounds the'fuel passing through the ports, said mixing plate means being of substantially planar construction and having preformed non-planar sections to permit predetermined and controlled thermal expansion, so that after the burner has been operated and the plate means heated, the plate means automatically assume their original position.

13. A high tum-down gas burner adapted to be disposed inand wheat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through Which-air from the air stream passes to produce air jets directed toward the burner fuel issuing through the fuel ports, apertures at the same distance from the fuel ports being staggered so that each air jet is directed toward and intercepts an imperforate portion of said one means so thatair from the air jets substantially surrounds the fuel passing through the fuel ports, said mixing plate means comprising a plurality of sections each of which is preformed to have a non-planar extending portion that permits the section, to thermally expand in a predetermined and controlled manner and contract to its original position without experiencing warpage.

14. A high turn-down gas burner adapted to be disposed in and to heat anair stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means extending generally obliquely forward and outward from said burner body means, said plate means defining a forwardly widening trough-shaped mixing space forwardly of said fuel ports, said mixing space being. forwardly wide open for free and open dischargecommunication with the passing air stream, said mixing plate walls projecting laterally of said burner body with their back faces positioned to lie exposed to the air stream flowing past the burner, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets, apertures at the same distance from the fuel ports being staggered so that each air jet is directed toward and intercepts an imperforate portion of said plate means so that the fuel jets are substantially surrounded by air, whereby the air jets are in offset relation to form a zipper flame pattern, said mixing plate means comprising a plurality of sections each of which is angulated to provide a peaked portion permitting thermal expansion and contraction of the section without causing any permanent warpage.

15. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially Within Which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets directed toward the burner fuel issuing through the fuel ports, apertures at the same distance from the fuel ports being staggered so that the air jets pass in opposite directions along opposite sides of the fuel passing through the ports so as to form a flame pattern of interlacing flames, protrusion means associated with certain rows of said aperture means for guiding air from the air stream directly into the flame pattern at intermediate and high firing rates, and said mixing plate means being preformed to permit predetermined and controlled thermal expansion, so that after the burner has been operated and the plate means heated, the plate means automatically assume their original position.

16. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of jets, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets, said aperture means being located in one or both of said means and one or both of said means being so constructed that the fuel jets are substantially looped by air from the air jets, the loops of air being disposed substantially in a plane that is substantially perpendicular to the axes of the fuel jets, whereby a pattern of interlacing flames is produced.

17. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of jets, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce air jets, said apertures being located in substantially opposing portions of one or both of said means such that said air jets pass by the fuel jets, contact said substantially opposing portions, and move along said opposing portions, whereby the fuel jets are substantially surrounded by air.

18. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes in the form of jets, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, channel means defined in one or both of said means including substantially oppositely facing sections that define a channel, means in said op positely facing sections defining a plurality of apertures through which air from the air stream passes to produce air jets, the spacing between said oppositely facing sec tions being such that the air jets pass by the fuel jets, extend across the channel, and are intercepted by said oppositely facing sections to cause the air jets issuing from said apertures to partially surround said fuel jets, whereby a pattern of interlacing flames having a zipper appearance is formed.

19. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce an array of air jets directed into the mixing space, said mixing plate means having a substantially planar construction and including bellows-like non-planar sections that provide predetermined bellows-like expansion in response to increased temperatures so that after the burner has been operated and the plate means heated, the plate means automatically assume their original position.

26. A high turn-down gas burner adapted to be disposed in and to heat an air stream, comprising a plurality of burner sections each of which includes burner body means, burner fuel ports defined in said burner body means and through which burner fuel passes, generally diverging mixing plate means supported from said body means to define a mixing space substantially within which said burner fuel and air from the air stream are intimately mixed to obtain complete combustion of said fuel, means in one or both of said means defining a plurality of apertures through which air from the air stream passes to produce an array of air jets directed into the mixing space, said mixing plate means being substantially planar and being connected at their ends to form a substantially continuous mixing plate structure, each of said plate means being provided with a preformed non-planar construction such that said mixing plate structure includes at regularly spaced intervals said preformed construction, said preformed construction providing substantially uniform expansion of said mixing plate means and thereby maintaining substantially uniform burner operation and uniform flame pattern irrespective of the temperature of the burner.

References Cited bythe Examiner UNITED STATES PATENTS 2,040,558 5/ 1936 Lukemeier 239-5535 2,959,355 11/1960 Houser 239397.5 3,051,464 8/ 1962 Yeo et a1. 239430 3,178,161 4/1965 Yeo et a1.

3,186,697 6/1965 Haedike et al.

M. HENSON WOOD, JR., Primary Examiner.

EVON C. BLUNK, Examiner.

R. S. STROBEL, Assistant Examiner. 

1. A HIGH TURN-DOWN GAS BURNER ADAPTED TO BE DISPOSED IN AND TO HEAT AN AIR STREAM, COMPRISING BURNER BODY MEANS, BURNER FUEL PORTS DEFINED IN SAID BURNER BODY MEANS AND THROUGH WHICH BURNER FUEL PASSES IN THE FORM OF JETS, GENERALLY DIVERGING MIXING PLATE MEANS SUPPORTED FROM SAID BODY MEANS TO DEFINE A MIXING SPACE SUBSTANTIALLY WITHIN WHICH SAID BURNER FUEL AND AIR FROM THE AIR STREAM ARE INTIMATELY MIXED TO OBTAIN COMPLETE COMBUSTION OF SAID FUEL, MEANS IN ONE OR BOTH OF SAID MEANS DEFINING A PLURALITY OF APERTURES THROUGH WHICH AIR FROM THE AIR STREAM PASSES TO PRODUCE AIR JETS, APERTURES AT THE SAME DISTANCE FROM THE FUEL PORTS BEING STAGGERED SO THAT EACH AIR JET IS DIRECTED TOWARD AND INTERCEPTS AN IMPERFORATE PORTION OF SAID ONE MEANS, WHEREBY THE AIR JETS SUBSTANTIALLY RING THE FUEL JETS TO FORM A PATTERN OF INTERLACING FLAMES HAVING A ZIPPER APPEARANCE. 